Onchocerciasis is caused by infection with a parasite Onchocerca volvulus.  It is also known as 'River Blindness' because the black fly that transmits the disease abounds in riverside areas.   It is endemic in Congo.  The treatment Mectizan is donated by the pharmaceutical company Merck & Co.  The company has pledged to continue to provide the drug completely free of charge for as long as it is needed. How amazing is that!